[Elecraft] Elecraft Digest, Vol 114, Issue 11

[David Cutter]

Thanks, Don, that was the reason for my question.  I've had dealings with
large MW motors and getting the right cables for them and in contrast low
voltage, high current applications.  Over here, once you get below the
Safety Extra Low Voltage (SELV) limit (meaning isolated and from memory
<42V) regime the rules change, but my memory fails me as to specifics.  I
have a feeling that the automotive industry have different insulation
requirements for instance.

David
G3UNA


----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "David Cutter" <d.cutter at ntlworld.com>
Cc: <elecraft at mailman.qth.net>
Sent: Tuesday, October 08, 2013 7:17 PM
Subject: Re: [Elecraft] Elecraft Digest, Vol 114, Issue 11


> David,
>
> I believe the same codes do apply since they are based on current, not 
> voltage.
>
> Codes aside, do not take low voltage, high current sources lightly 
> (particularly batteries) because they are a very large source of energy. 
> If shorted, molten metal spewing all over is not an exaggeration, it is 
> real.
> That is why the power cables should be fused for the Ampacity rating of 
> the wire with the fuse placed near the power source.  You are protecting 
> the wire against fault conditions, not necessarily the equipment 
> connected.
>
> Shock hazards are a different thing - fuses will not help with shock 
> hazards.  True, low voltage supplies may not be a shock hazard, but they 
> are a hazard just the same because of the high energy available should 
> there be a fault.
>
> 73,
> Don W3FPR
>
> On 10/8/2013 1:45 PM, David Cutter wrote:
>> Are those codes applied to low voltage isolated supplies by law or
>> are there separate codes for this?  In the context of the original 
>> question, the 13.8V dc supply will not have the same shock hazard, though 
>> it may have the same fire hazard, so, perhaps a different code/standard 
>> applies.  House wiring requires a high degree of safety because its 
>> potential (risk) for fire, but the risk of fire in isolated low voltage 
>> equipment which is on view (ie not hidden in building cavities etc) is 
>> different.
>